I may be new to forex trading, but when i see an overly simplistic statement like the title to this thread i know exactly why 90% of traders lose money.
First money doesn't appear out of thin air, so if somebody wins big, somebody has to lose big or many have to lose a small amount. Although there is some natural inflationary growth to be gained.
Second there are many ways to make a bad trade but a good trade has to be made with accuracy and skill.
That skill cannot be acquired with a few simple lessons. It is acquired after thousands of hours of dedicated learning and hard work to be in that top 10%. If you only had to reach a moderate standard to be successful and everyone could make money where would the money come from. where are the losers. Then even if you put a group of people through a college degree in trading it would improve those that completed the courses chances greatly, but some would still fail because they did not have they mental aptitude to succeed when there own real money was on the line.
My own success strategy is to only rely on what i know works for myself.
To practice on demo accounts until i can sustain demo account growth over long term periods. I expect this to take more than 2 years. then transition carefully to live accounts to see if I can manage the psychology of real trading.
While fundamental and technical analysis plus psychological skills are important, a long term vision as to what it takes to succeed is even more important.